Heretofore, as a contact device, there has been known one in which a movable contactor is arranged on one end portion of a drive shaft that reciprocally moves in an axial direction based on magnetization and demagnetization of an electromagnet block (for example, refer to Patent Literature 1).
In this Patent Literature 1, movable contact points, which individually contact and leave a pair of fixed contact points provided in parallel to each other, are provided on both end portions of the movable contactor, and the movable contact points are configured to contact and leave the fixed contact points following movement of the movable contactor.
Then, the movable contactor is sandwiched by a first yoke and a second yoke, whereby a magnetic circuit is formed between the first yoke and the second yoke. In this way, a malfunction is solved, which is caused by electromagnetic repulsive force acting between the fixed contact points and the movable contact points in an event where an abnormal current flows in a contact point ON state.
The malfunction, which is caused by the electromagnetic repulsive force acting between the fixed contact points and the movable contact points, specifically refers to a problem as described below.
When the abnormal current flows in the contact point ON state, and the electromagnetic repulsive force acts between the fixed contact points and the movable contact points, then a contact point pressure is lowered, and a contact resistance is increased, resulting in a sharp increase of Joule heat, and the contact points are opened and separated from each other, resulting in generation of arc heat. Therefore, it is apprehended that the movable contact points and the fixed contact points may be welded to each other.
However, if the first and second yokes are provided on the movable contactor, then the first and second yokes generate magnetic force to suck each other based on the abnormal current flowing in the contact point ON state, and become able to regulate such an operation that the movable contactor is going to be opened and separated from the fixed contact points. Then, this regulation of the operation that the movable contactor is going to be opened and separated from the fixed contact points allows the movable contact points to stick to the fixed contact points without allowing the movable contactor to repel the fixed contact points, and accordingly, an occurrence of an arc is suppressed.
As described above, in Patent Literature 1, the first and second yokes are provided on the movable contactor, whereby an overcurrent capacity is increased, thus enabling to suppress the contact points from being welded to each other owing to the occurrence of the arc.